1 What is ocean sound?

Ocean sound refers to the collection of acoustic energy present in marine environments, encompassing a variety of sources, including sounds from marine animals, geophysical noise from waves, wind, rain, and human generated sounds from shipping, sonar, and offshore construction. This collection of sound at a given place and time is often called a soundscape. Monitoring ocean soundscapes provides key insight to understanding ecosystem dynamics, detecting environmental changes, and managing the impacts of noise pollution on marine organisms. Learn more about ocean sounds at Discovery of Sound in the Sea.

Why do we care? Ocean sound is critical for the survival of many marine animals because it is a primary means of communication, orientation and navigation, finding food, avoiding predators, and choosing mates. As such, human activities that produce underwater sounds have the potential to negatively impact animals by reducing their ability to hear prey, predators, and each other. U.S. national marine sanctuaries are home to many acoustically active marine animals and understanding the presence and impacts of noise is a conservation priority. Further, the occurrence and types of sounds present offer key insights on animal presence, species behaviors, human-use patterns, and changing ocean conditions.

Where are we listening? NOAA’s Office of National Marine Sanctuaries (ONMS) maintains a nationally coordinated underwater sound monitoring network, known as ONMS Sound. ONMS sound works with partners to monitor ocean sound off the US East, West, and Gulf Coasts and in the Pacific Islands region. Ocean Sound monitoring sites are placed in strategic locations within sanctuary boundaries. Data from the sound monitoring sites are available through the NOAA National Centers for Environmental Information’s Passive Acoustic Archive. Explore the ONMS sound and partner monitoring sites here.

Purpose of a soundscape inventory report This report provides regular updates on ONMS ocean sound monitoring efforts. The report includes basic summary graphics and tables to understand the soundscape and provide indicators of change. The report represents analyses that are maintained by ONMS sound. If partners are maintaining analyses, those results are also included (e.g. species detections by NMFS). We also highlight key insights from specific dedicated studies that used these data.

2 Ocean sound monitoring in Stellwagen Bank National Marine Sanctuary

The Stellwagen Bank National Marine Sanctuary is a wild ocean place near an urban world, sits east of Boston, Massachusetts between Cape Ann and Cape Cod. Historically important as a fishing ground, New England’s only national marine sanctuary now reigns as a premier whale watching destination and continues to support commercial and recreational fishing.

The history of ocean sound monitoring within SBNMS began with a focus marine mammal sounds, including the endangered North Atlantic Right Whales.Noise reduction during vessel speed reduction programs is also well studied in this region.

Current ocean sound monitoring is maintained at four sites within SBNMS. Three sites (SB01,SB02,SB03) are located more inshore, capturing more local vessel activity and sounds from nearshore species. One offshore sites (NRS09) captures patterns in migrating whales and transiting commercial vessel traffic and is part of the US Ocean Noise Reference Station Network.

Summary of ocean sound monitoring sites
Site Primary.monitoring.purpose Oceanographic.Setting Depth Seasonality Vessel.Traffic.Setting Latitude Longitude TotalDays StartDate Information
SB01 To monitor a site that supports seasonally high abundances of Atlantic cod and is located near a region of elevated commercial vessel activity. Continental shelf (<200m) 50 m Seasonal winds and baleen whales presence near inbound TSS lane to Boston, within existing Off Race Point SMA slowing large traffic in March-April 42.43855 -70.5458 852 2018-11-12 https://sanctsound.portal.axds.co/#sanctsound/sanctuary/monterey-bay/site/SB01
SB02 Part of Sanctuanry Soundscape Monitoring Project (2018-2022) Continental shelf (<200m) 68.3 m Seasonal winds and baleen whales presence NA 42.47000 -70.2300 NA 2018-11-12 https://sanctsound.portal.axds.co/#sanctsound/sanctuary/monterey-bay/site/SB02
SB03 To monitor shallow sandy habitat situated on the bank that supports the foraging and social activities of marine mammals. Continental shelf (<200m) 45 m Seasonal winds and baleen whales presence near outbound lane to Boston and within Off Race Point SMA slowing large traffic April-May; illegal scalloping in March-April 42.25557 -70.1788 1708 2018-11-12 https://sanctsound.portal.axds.co/#sanctsound/sanctuary/monterey-bay/site/SB03
NRS09 To continue long-history of monitoring trends in ocean noise, including cetacean species presense and vessel movement Continental shelf (<200m) 79 m Seasonal winds and baleen whales presence fan of traffic moving north to Canadian ports, but more distant/dispersed 42.40000 -70.1300 2701 2014-10-21 https://www.pmel.noaa.gov/acoustics/noaanps-ocean-noise-reference-station-network

3 What is the soundscape in SBNMS ?

A soundscape includes all the different sounds present at a given time and location. How do we visualize this information? One way is to indicate the main sound contributors on a frequency by sound level graphic, known as spectral plot. The seasonal differences are shown as the colored lines. The known sources of interest in this soundscape are indicated by vertical lines and shaded areas at specific frequency(s). Wind noise occurs within an expected range and is represented the black lines. We can track these different contributions to understand how a soundscape is changing. We can also compare across locations.

A visualization of ocean sound. Seasonal summary of measured sound levels (colored lines) shown as median hourly values over all available data. Vertical lines indicate representative frequencies for different sound sources. The bottom bar shows how the data are distributed in the different wind categories: low < 5 m/s, med 5-10 m/s, high >10 m/s. Dotted lines are modeled wind noise at this depth based onHildebrand et al 2021.A visualization of ocean sound. Seasonal summary of measured sound levels (colored lines) shown as median hourly values over all available data. Vertical lines indicate representative frequencies for different sound sources. The bottom bar shows how the data are distributed in the different wind categories: low < 5 m/s, med 5-10 m/s, high >10 m/s. Dotted lines are modeled wind noise at this depth based onHildebrand et al 2021.

The median power spectral densities (PSD) for all hours across all years are calculated from calibrated audio data using community software tools: Triton Soundscape Metrics, MANTA, or PyPAM. Triton software calculates the one-third octave band sound pressure levels by integration of PSD levels with a 1 Hz/1 second resolution and a median was used to calculate hourly values over no less than 1,800 1-s values for that hour and converted to decibels (dB re 1 μPa). MANTA and PYPAM software calculates power spectral density (PSD) levels per minute (μPa²) within the hybrid milledecade frequency bands. PAMscapes was used to calculate the median for each hour within one-third octave bands. These values were then converted to 1-Hz resolution to match the wind model results by converting to pressure and dividing by the band width before converting back to sound spectrum levels in decibels (dB re 1 μPa/Hz).

No one soundscape is alike and we can use other sites in similar oceanographic settings (e.g. nearshore or offshore) to compare conditions. From 2018-2022, the U.S. National Oceanic and Atmospheric Administration (NOAA) and the U.S. Navy engaged in a multi-year effort to monitor underwater sound within the U.S. National Marine Sanctuary System, known Sanctuary SoundScape Monitoring Project. Data collected during this dedicated period provide initial insights on how soundscapes compare.

A comparison of soundscapes. Curve in black represents current location.A comparison of soundscapes. Curve in black represents current location.

4 What are the latest conditions in ocean sound?

Soundscapes are dynamic, changing with season and annual differences in sources (wind, biologics, and human-activity). Comparing annual ocean sound levels provides insights on trends in ocean sound: Are levels lower in the most recent year of monitoring? Efforts to reduce noise are underway on global to local scales though vessel speed reduction strategies and engineering solutions, and these efforts may be be reflected in the annual data. Typically, a more focused analysis is necessary to tease apart the multiple drivers of ocean sound levels.

Annual comparison of ocean sound.Annual comparison of ocean sound.

5 How often is ocean sound above wind conditions?

If sound levels are above what is expected for wind, other sources are likely contributing to the soundscape. The percent of the time above wind lets us know how often a sound is present. The decibels above lets us know how much sound is added. It is best to look at time above within specific frequencies of interest.

100 Hz represents low-frequency ship noise. In many marine environments, ships are transiting the region for a variety of purposes (e.g. transporting goods, harvesting ocean resources, and carrying tourists). When these ships are transiting noise is added to the soundscape, particularly in the lower frequencies.

A comparison of soundscapes. Curve in black represents current location.A comparison of soundscapes. Curve in black represents current location.

6 How often do nearby ships contribute noise to the soundscape?

Only results from sites with AIS data in 10 km buffer included in this section.

How much noise do nearby ships contribute to the soundscape?

7 How much do vessel speed reduction programs reduce ocean noise?

Only results from sanctuaries with an active VSR program analyzed for this section.

8 When do biological sounds contribute to the soundscape?

Only results from sites with species detections included in this section.

9 What are we learning?

We continue to discover even more from these ONMS ocean sound data. Collaborative partnerships help us gain key insights on sanctuary resources and conditions from ocean sound data by leveraging ecological and technological expertise. Here are a few recent examples: